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Effects of H_2O and CO_2 on magma generation in the crust and mantle

Wyllie, P. J. (1977) Effects of H_2O and CO_2 on magma generation in the crust and mantle. Journal of the Geological Society, 134 (2). pp. 215-234. ISSN 0016-7649. http://resolver.caltech.edu/CaltechAUTHORS:20160217-110854084

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Abstract

The solution of H_2O, CO_2, and H_2O–CO_2 mixtures in silicate magmas has many effects. Fusion temperatures are lowered, and the fusion and crystallization sequences may be modified. Hydrous minerals and carbonates may become stable within the fusion interval. Liquid compositions are changed as a function of dissolved volatile content, and as a function of H_2O/CO_2. The physical properties of magmas may be influenced markedly by dissolved volatile components. The presence of vapour bubbles arising from exsolution of volatile components during uprise or crystallization of magma may be responsible for physical and geochemical effects. These effects are outlined by examination of the phase relationships in several synthetic systems and rock–H_2O–CO_2 systems. The results demonstrate that H_2O is more influential than CO_2 in magma generation at crustal pressures. The presence of CO_2, however, may influence the evolutionary history of a crustal magma body. In the mantle at depths of 75–80 km, the influence of CO_2 becomes as significant as that of H_2O because CO_2 reacts with peridotite stabilizing calcic dolomite, and the solubility of CO_2 increases dramatically. The compositions of near-solidus mantle magmas are strongly influenced by H_2O/CO_2 and by the distribution of carbonate, amphibole and phlogopite in the peridotite. The normal product of crustal anatexis is H_2O-under-saturated granitic liquid. Tonalite liquids can-not be produced by crustal anatexis during normal regional metamorphism.


Item Type:Article
Alternate Title:Effects of H2O and CO2 on magma generation in the crust and mantle
Additional Information:© 1977 Geological Society of London. Received November 26, 1976. This research was supported by the Earth Sciences Section, National Science Foundation, NSF Grants EAR 76-20410 and EAR 76-20413. We would like to acknowledge also the general support of the Materials Research Laboratory by the National Science Foundation.
Funders:
Funding AgencyGrant Number
NSFEAR 76-20410
NSFEAR 76-20413
Record Number:CaltechAUTHORS:20160217-110854084
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160217-110854084
Official Citation:P. J. WYLLIE Effects of H2O and CO2 on magma generation in the crust and mantle Journal of the Geological Society, v. 134:215-234, doi:10.1144/gsjgs.134.2.0215
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64537
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:19 Feb 2016 19:15
Last Modified:19 Feb 2016 19:15

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